Is there a way to mask part of a video clip in the Shading editor?

What I’m trying to do is edit it so it appears he is flying the butterfly. I can combine them on the compositor and use the keying node to remove the greenscreen, but It’s very hard to line the clips up with any precision there. I basically just want to crop a small part at the bottom of the Dany DeVito clip to make it look more like he is inside the butterfly’s wings, but I can’t figure out how to mask in the shading editor.